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Module 2: Week 1 Introduction to Palaeozoic Britain Old Lost Sea: The Iapetus Ocean Wikimedia Commons
Transcript

Module 2:Week 1

Introduction to Palaeozoic Britain

Old Lost Sea: The Iapetus Ocean

Wikimedia Commons

Palaeozoic periods

Permian (299–252 Ma)

Carboniferous (359–299 Ma)

Devonian (419–359 Ma)

Silurian (444–419 Ma)

Ordovician (485–444 Ma)

Cambrian (541–485 Ma)

North-South dividePalaeozoic UK partitioned into ‘terranes’:

Scotland, N. Ireland = ‘Laurentian’ (North American)

England, Wales, S. Ireland = Avalonian (Euro-Africa)

Dividing the Early Palaeozoic

V

(Images from Wikimedia Commons)

Rev. Adam Sedgwick

Sir Roderick ImpeyMurchison

Uniting the Early Palaeozoic

Charles Lapworth Charles Walcott

Not to mentionJ. Tuzo Wilson

RichardFortey

RobinCocks

The Cambrian Controversy

Sedgwick vs Murchison

1835: collaboration

&

(Images from Wikimedia Commons)

Sedgwick - Cambrian

Murchison- Silurian

Cambria

Sedgwick studiedgeology of North Wales

Siluria

Murchison studied geology of South Wales

1839-1873:competition

V

(Images from Wikimedia Commons)

Murchison began

encroaching his ‘Lower

Silurian’ on Sedgwick’s

‘Upper Cambrian’

1879: compromise

(Images from Wikimedia Commons)

Lapworth proposes the Ordovician

Cambrian outcrops (Eng & Wal)

Harvey et al. (2011)

Walcott's Cambrian critters

Walcott's Cambrian critters

Puzzling distribution of Euro-American fossils

Wilson's (1966) wonderings

Did the Atlantic close then re-open?

Cocks & Fortey (1982)

Fossils = more precise timings

Cambrian: very differentLaurentia & Avalonia far apart

Ordovician = getting similarL & A converging

Silurian = very similarL & A converged

Wilson Cycles?

Cyclical plate tectonic system

by which oceans open and close

Start of a Wilson Cycle

Hot spot → rifting beneath continent

Middle of a Wilson Cycle

ACTIVE margin PASSIVE margin

End of a Wilson Cycle

Subduction of ocean → continental collision

Late Precambrian

opening of Iapetus Ocean

Start of a Wilson Cycle

Precambrian supercontinent break-up

Cambriangeography

© Ron Blakey (Geosystems)http://cpgeosystems.com/paleomaps.html

Early-Mid Cambrian (Eng & Wal)

Cambro-Ordovician (Eng & Wal)

Hebridean Terrane, NW Scotland

Cambro-Ordovician Scotland

Cambro-Ordovician

strata, Northwest Scotland

Sea-level change

controlled deposition?

Middle of a Wilson Cycle

ACTIVE margin(Eng & Wales)

PASSIVE margin(Scotland)

Late Cambrian

Early CambrianPASSIVE margin

(Scotland)PASSIVE margin(Eng & Wales)

Early Ordovician

Mid-Ordovician

Late Ordovician

Ordovician volcanism

Borrowdale Volcanic Group

Fiamme textures in ignimbrite, Great Paddy Crag, Buckbarrow

© BGS

Late-stage Wilson Cycle

ACTIVE marginAvalonia

North Wales

West Wales

Lake District

Death of an ocean

Silurian: The closing of Iapetus

LinksPalaeogeographical maps of Europe:http://cpgeosystems.com/euromaps.html

The Wilson Cycle:http://csmres.jmu.edu/geollab/fichter/Wilson/Wilson.html

The Iapetus in Newfoundland:http://theindependent.ca/2011/06/14/gros-mornes-old-lost-sea/


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